Fig. 4

Effects of a tibiotarsus malalignment on the kinematics of the intertarsal joint (ITJ) in the right leg of a Curlew (SMF 499; Senckenberg Research Institute). a Tibiotarsi of the handicapped bird; cranial view of the normal left (L) and caudo-lateral view of the misaligned right (R) bone that shows the canal through the ossified callus. b–g 3D models of the left (yellow) and right (blue) tibiotarsus and tarsometatarsus, with extended (b–d) or flexed (90°; e–g) ITJ (scale reduced to 65% of that in a). The bones of the malaligned right leg are mirrored (turning them into left leg bones geometrically), and the proximal part of the normal tibiotarsus was superimposed on the malaligned tibiotarsus to directly visualize the geometric effects of the deformity. c, f Cranial views; b, e medial views (from the right); d, g lateral views (from the left). Compare Additional file 2: Video S2, Additional file 3: 3D model S1 and Additional file 4: 3D model S2